The present invention relates to a system for retaining documents such that withdrawal and replacement of the documents from the retainer is sensed through the use of an electrical circuit and contacts incorporated into the retainer. In a more specific example, the present invention relates to the protection from loss of credit cards using a so-equipped wallet or purse.
At present the most common retainers for documents are file cabinets, brief cases, folders, purses and wallets. These retainers are intended to be used for organized storage and physical protection of documents and provide varying degrees of capacity, portability and security. With these retainers it is however, quite common for the user to forget to place the documents back into the retainer after use. As a result and most commonly with respect to credit, bank transaction and personal identification cards, the documents are left behind at point of use where they are particularly prone to loss, theft and misuse.
There have been several previous attempts at solving this problem. In particular, U.S. Pat. No. 3,959,789 discloses a credit card carrying case which incorporates contacts attached to the inside surfaces of separators adapted to hold credit cards and to detect the absence of a card. However, problems exist in this design in that the case is very bulky and uses a single external spring clip to bias the multitude of pairs of separator contacts together. The use of the single spring clip results in the contact pressure being spread over too wide an area thereby reducing the sensitivity of the device making the sensitivity too low for reliable detection.
U.S. Pat. No. 4,480,250 discloses a credit card carrier in which a series of clip switches bridge from the hinge or spine of a pair of folding flaps to common conductor strips, one strip being located on each side flap. An alarm is triggered if the edge of any card is not held between the assigned clip switch contacts when the flaps are folded to overlie one another, due to the closing of a magnetic proximity switch provided on the outboard edges of each flap. However problems exist in this design in that the edge to edge card holding layout is inconvenient in terms of space and area required per card. Furthermore, no facility is provided to guide the cards into position between the clip switch contacts nor to prevent them from falling out of position. In addition, the magnetic proximity switch is fragile, imprecise and difficult to align if the holder is flexible. Also, the magnetic switch might endanger the magnetic code strip common to most modern credit and bank cards.
U.S. Pat. No. 4,652,865 discloses a credit card holder composed of partly transparent pockets with conductive strips and/or disk-shaped magnetic contacts attached to the inside surfaces of the pockets in opposed alignment. The strips or contacts detect the withdrawal of credit cards and electrically activate an alarm system composed of a battery, buzzer and timer. In one embodiment, leaf springs are provided inside double layered pocket walls to urge the walls and attached contacts together. In another disclosed embodiment, the pockets are configured in book leaf form or edge to edge fold-up accordion fashion. However, problems exist in this device in that the use of the magnetic contacts may damage magnetic card coding provided on credit or bank cards. Furthermore, the leaf springs positioned between pocket lining layers may cause bulging of the pockets and without solid anchoring or support, may not provide sufficient force for reliable sensor contact pressure and function.
U.S. Pat. No. 4,692,745 discloses a holder for credit cards with an alarm circuit triggered by the withdrawal of a card from a receptacle and the subsequent closure of the holder. A light sensitive switch is used to prevent current flow to the alarm circuit when the holder is in the open position. Each set of card contacts is attached to a separate bracket thereby making the holder somewhat bulky. Many scenarios are envisioned wherein, if the holder is not fully closed and the light sensor is exposed when a card is missing, the alarm fails to sound, resulting in a lapse of the intended function of the device and loss of the card.
U.S. Pat. No. 4,719,453 discloses a wallet with an alarm actuable in a manner similar to that disclosed in U.S. Pat. No. 4,692,745. The card sensing means includes a plurality of clip switches arranged to be interconnected in parallel on a card plate.
U.S. Pat. No. 4,721,948 discloses a wallet with credit card holder that utilizes a flat flexible magnetic strip upon which two flat parallel conductors are insulatedly attached. Co-attractive conductive ferrous chips are opposingly attached to the inside of the far pocket walls such that the near pocket walls, which overlie the conductors, have openings to allow the chips clearance to attract magnetically into contact with the conductors upon withdrawal of a credit card. The chip bridges the conductors and closes the alarm circuit. The sensor function is completely dependant upon the magnetic attraction of the ferrous chips to the magnetic strips. Again problems exist in that damage may occur to the magnetic code provided on cards due to the magnetism. Moreover, the ferrous chip materials are subject to oxidation and subsequent poor conductivity.
Australian Patent No. AU-B-46568/85 discloses a security holder for a credit card with an alarm that senses the absence of cards from clip-switch-equipped receptacles. Each receptacle has a separate and structurally independent pair of clip switch contacts. The electric circuits disclosed in this reference include, in addition to receptacle sensors, a series connected timer with a hand holding pressure sensor operable to suppress the circuit function as well as a holder closure sensor. However, problems exist in this device in that if the contacts are arranged as disclosed with all the pairs overlapping each other, the resulting holder is quite bulky and complex to assemble. Also, the user must carefully fit the cards between the exposed clip switch leaf ends as there has been no consideration for passive guidance of the card between the clip switch contacts.
It is therefore an object of the present invention to provide a novel document retainer.